There is currently interest in the detergent industry in concentrated detergent products. These products provide advantages to the consumer, who has a product which can be used in lower amounts and is more easily stored, and to the producer and intermediates, who have lower transportation and warehousing costs. A major difficulty, though, is finding a relatively inexpensive and efficient way to produce a condensed detergent granule for inclusion in a concentrated detergent product.
The traditional method for producing detergent granules is spray drying. Typically, detergent ingredients such as surfactant, builder, silicates and carbonates are mixed in a mix tank to form a slurry which is about 35% to 50% water. This slurry is then atomized in a spray drying tower to reduce moisture to below about 10%. It is possible to compact spray dried particles to make dense detergent granules. See U.S. Pat. No. 4,715,979, Moore et al., issued Dec. 29, 1987. However, the use of spray drying to make condensed granules has some disadvantages. Spray drying is energy intensive and the resulting granules are typically not dense enough to be useful in a concentrated detergent product. Spray drying methods generally involve a limited amount (less than 40%) of organic components such as surfactant for environmental and safety reasons.
Other technologies for producing a dense detergent granule are described in the following patent applications.
Japanese Patent 61-118500, Hara et al., laid open Jun. 5, 1986, discloses a method for the manufacture of concentrated detergent compositions characterized by kneading the materials of the detergent composition continuously, and feeding these materials, which contain at least 30% by weight of surfactant, into an airtight-type kneader with a controlled pressure of 0.01-5 kg/cm.sup.2 G.
Japanese Patent 62-263299, Nagai et al., laid open Nov. 16, 1987, discloses a method for the preparation of granular nonionic detergent compositions by first forming a solid detergent by kneading and mixing uniformly a raw material mixture consisting of 20-50 weight % of nonionic surfactant, which is a liquid or a paste, at a temperature not about 40.degree. C. and 50-80 weight % of a mixture of (A) a zeolite, and (B) a lightweight sodium carbonate in the ratio of (A)/(B)=75/25-25/75 by weight, followed by granulation of the solid detergent. Mechanical granulation (grinding) follows the kneading step.
Japanese Patent 61-231099, Sai et al., laid-open Oct. 15, 1986, discloses concentrated powdered detergents containing (a) anionic surfactant, (b) polycarboxylic acid polymer or their salts, (c) polyethylene glycol, wherein the amount of (a) is 25-50% by weight and the total amount of (b) and (c) is 2-10% by weight, while the ratio of (b) to (c) is 1/3 to 6/1. The detergent also contains 0-10% by weight of a water-soluble neutral inorganic salt. A grinding process for obtaining the product is mentioned (page 7).
Japanese Patent 60-072999, Satsusa et al., laid open Apr. 25, 1985, discloses a production method for a highly concentrated powder detergent where sulfonate and/or sulfate is mixed with sodium carbonate and water in a high shear mixer, cooled below 40.degree. C., and then pulverized with a zeolite powder and other detergent components.
Japanese Patent 62-45696, Mukoyama et al, laid open Feb. 27, 1987, disclosed a dense granular detergent composition made by mixing and pulverizing a detergent composition which is then coated with water-insoluble micropowder (5-35% zeolite).
Certain problems are associated with using mechanical methods such as grinding, crushing or extruding to form detergent granules. As the temperature in the grinding, crushing or extruding mechanism rises, buildup, smearing and sieve screen blinding can occur. Humid air conditions can also increase buildup of the detergent materials in the equipment. These problems generally are worse with higher levels of organic material in the composition.
U.S. Pat. No. 4,515,707, Brooks, issued May 7, 1985 discloses anhydrous fatty alcohol sulfuric acid or ethoxylated fatty alcohol sulfuric acid which is neutralized with dry sodium carbonate powder in the presence of powdered sodium tripolyphosphate in a high shear mixer. The dry, powdered, neutralized reaction product is stored until require for use in the manufacture of a detergent bar whereupon the powder is mixed with liquid ingredients for the detergent bar and subjected to conventional manufacturing steps for a detergent bar.
Canadian Patent 1070210, Schoenholz et al, issued Jan. 22, 1980 discloses a dry blended, concentrated detergent composition of a surfactant compound and a dense powdery composition consisting essentially of a certain carbonate and from 0 to 40% other miscellaneous additives.
European Patent Application 266847-A disclosed production of an organic acid containing, pliable, pasty detergent composition comprising dry mixing a linear alkyl benzene sulphonic acid with sodium carbonate, neutralizing the mixture with caustic solution to form a pasty mass, and blending with active organic acid and filler. It is said that these compositions are useful for incorporation into multiple use scrubbing pads for bathroom use, etc., for removing soap scum and lime scale. It is also said that the order of addition of components gives the desired pasty mass.
Pending U.S. patent application Ser. No. 213,575, Strauss et al., filed Jun. 29, 1988, now U.S. Pat. No. 4,925,585, relates to a process for making a free flowing granular detergent comprising (a) mixing an effective amount of an aqueous surfactant paste having a detergency activity of at least 40% and an effective amount of a dry detergency builder, said surfactant paste active and builder having a ratio of 0.05:1 to 1.5:1; (b) rapidly forming a uniform dough from said mix at a dough temperature of from about 15.degree. C. to about 35.degree. C.; (c) cooling said dough to a granulation temperature of from about -25.degree. C. to about 20.degree. C.; and (d) granulating said cooled dough into discrete detergent granules using fine dispersion mixing at a tip speed of about 5-50 m/sec.
Pending U.S. patent application 288,759, Strauss et al., filed Dec. 22, 1988, relates to a process for making concentrated surfactant granules from a high active surfactant paste using fine dispersion granulation. The process comprises:
A. mixing surfactant paste having about 50% detergency activity; PA0 B. cooling the paste to a granulation temperature of about -65.degree. to 25.degree. C.; PA0 C. granulating the cooled paste into discrete surfactant granules using fine dispersion mixing at a mixing tip speed of about 5-50 m/sec. for about 0.1 to 10 minutes. PA0 (a) forming a doughy mass comprising a substantially uniform mixture of, by weight: PA0 (b) mixing the doughy mass with an effective amount of a deagglomerating agent, which is a fine powder having a mean particle size of less than about 200 microns, in a high shear mixer at a tip speed of greater than about 10 meters per second and wherein the ratio of doughy mass to deagglomerating agent added in step (b) is from about 9:1 to about 1:5.